MAC in MAC, MinM for short, is a technology for provider backbone bridging put forward by IEEE 802.1ah. This technology provides a solution to users' Ethernet service transport in an Ethernet metropolitan area network or a wide area network. It may be compatible with the existing Ethernet metropolitan area networks or wide area network devices, protect the existing backbone bridging devices of the providers and the investment of edge Ethernet access devices of the providers. A network that supports MAC in MAC technology is called MAC in MAC network for short. Ethernet employs MAC in MAC encapsulation mode, so that the security and extensibility of Ethernet may be improved. The public network of MAC in MAC layer 2 backbone network is the management domain of the provider, and it consists of a MinM edge device-provider backbone bridging device (PBB) and a backbone network device (PB). The PBB is used for accessing a service of a user private network via a MinM tunnel, the PB is used for bearing a MinM tunnel.
MinM technology may well resolve the problem of the rapid expansion of MAC address in the provider's Ethernet, and the problem of limitation of service instances in the existing switching (QinQ) access mode, as well as the problems of MAC address multiplexing, user protocol message transparent transmission and remote flow mirroring and the like. QinQ is an Ethernet standard supporting two layers of virtual local area network tags (VLAN TAG) defined by IEEE 802.1ad, which is used by a provider to provide transparent transmission of VLAN.
Ethernet transport service provided by MinM technology is a unicast service based on MAC in MAC tunnel. MinM technology may not provide a good solution to multicast service.
At present, the method for implementing multicast in MinM technology includes copying a multicast message in a custom edge (CE) device by which the multicast source provides a service instance in accordance with the number of the users applying for the service instance in a multicast group, and transporting each copied multicast message to the destination user via its respective MAC in MAC tunnel.
In view of the method for implementing multicast in the existing MinM technology, the point-to-multipoint multicast provided actually transports unicast messages over the backbone network; in other words, multiple copies of multicast messages are transported over the backbone network via different MAC in MAC tunnels respectively, and multicast is processed as unicast in the prior art, and therefore a huge occupation of bandwidth is caused. Moreover, as the proportion of the multicast flow in the network becomes larger and larger, there are more and more multicast sources, and the number of multicast messages copied by each multicast source becomes larger and larger. As a result, more occupation of network bandwidth will be caused when the method of the prior art is employed.